1. Field of the Invention
The present invention relates to novel naphthopyran-type compounds that have, in particular, photochromic properties. The invention also relates to photochromic compositions and photochromic ophthalmic articles (goggles, lenses and eye-shields, for example) that contain these naphthopyrans. The invention also covers the preparation of these novel naphthopyrans. The photochromic compounds are capable of changing color under the influence of a first poly-chromatic or mono-chromatic range of luminous radiation (UV radiation for example) and of returning to their initial color when the luminous irradiation ceases, or under the influence of temperature and/or poly- or mono-chromatic light different from the first light. The invention particularly relates to naphthopyrans having a benzodioxine group fused to the naphthalene core.
2. Background of the Art
Photochromism generally concerns the ability of a compound to reversibly change color under different light conditions. One particular type of photochromic phenomenon concerns the reversible change in color of a compound from an original color to a different color when the compound is exposed to a source of ultraviolet radiation, such as solar radiation or light radiated from a mercury or xenon lamp. The photochromic compound fades to the original color within a period of time after the photochromic compound is isolated from the ultraviolet radiation This can be done, for example, by placing the compound in a dark room.
Photochromic compounds find applications in various fields, such as for the manufacture of ophthalmic lenses, contact lenses, solar protection glasses, goggles, sun screens, filters, camera optics, photographic apparatus optics or other optical devices and observation devices, glazing, decorative objects, currency elements and even for information storage by optical inscription (coding). For example, photochromic compounds, such as naphthopyrans, are incorporated into plastic ophthalmic lenses to effect color changes in the lenses when the lenses are exposed to particular lighting conditions. Additionally, different photochromic compounds may be blended together to create a color effect that is different from respective color effects of the individual photochromic compounds. As an example, a first photochromic compound that turns orange or red when activated by light and a second photochromic compound that turns blue when activated by light may be blended together to form a photochromic mixture that produces a shade of gray when activated by light.
In the field of ophthalmic optics, and in particular the field of spectacles, a photochromic lens that comprises one or more photochromic compounds is usually required to have:                a high transmission level in the visible region in the absence of ultraviolet radiation,        a low transmission (high colorability) under solar irradiation (especially with ultraviolet radiation exposure),        desired coloration and discoloration kinetics, e.g., high sensitivity to irradiation and fast bleaching,        a high solubility in hosting materials,        a tint acceptable to the consumer (gray or brown preferably) with the chosen tint maintained during the coloration and the discoloration of the lens,        a maintenance of the performance and properties, within a temperature range of 0-40° C.,        a significant durability, since these objectives sought after are used in sophisticated corrective lenses and are therefore expensive.These lens characteristics are primarily determined by the active photochromic compounds. These compounds must furthermore be compatible with the organic or inorganic support that constitutes the lens.        
Moreover, it is to be noted that obtaining a neutral, gray or brown tint may necessitate the use of at least two photochromes of different colors, i.e., two separate compounds having distinct maximal absorption wavelengths in the visible region of the electromagnetic spectrum. The use of combinations of photochromic compounds imposes other requirements on both the individual photochromic compounds and the groups of photochromic compounds combined. In particular, the coloration and discoloration kinetics of the (two or more) combined active photochromic compounds must be essentially identical. The same applies for their stability with time, and also for their compatibility with a single plastic or inorganic support.
Amongst the numerous photochromic compounds described in the prior art, benzopyrans or naphthopyrans are described in patents or patent applications U.S. Pat. Nos. 3,567,605; 3,627,690; 4,826,977; 5,200,116; 5,238,981; 5,411,679; 5,429,744; 5,451,344; 5,458,814; 5,651,923; 5,645,767; 5,698,141; 6,018,059; 6,296,785; WO-A-95 05382; WO-A-96-14596; WO-A-97 21698 which are of the reduced formulae below: U.S. Pat. Nos. 5,651,923 and 6,018,059 more specifically describe naphthopyrans having benzofurano or naphthofurano groups fused to the naphthalene ring of naphthopyran (the general structures are shown below). The various substitutent groups are defined in the various patents and encompass a wide, art-accepted range of combinations of substitutents intended to provide specific physical or photochromic properties. These compounds claim to satisfy the specifications identified above as needed for photochromic compounds. In reality, even if these compounds really do have one or more of the basic properties sought after, such as a high transmission in the absence of ultraviolets and a high colorability under solar irradiation, none of the compounds described hitherto have the complete combination of properties necessary for the production of satisfactory articles. In particular, none of these compounds is intrinsically gray or brown, and the necessity of using an additional photochromes in order to obtain one of these two tints does persist.
In this context, it is to the credit of the applicants to have been interested in this type of derivatives as a base for developing novel photochromes, and for having found, in a surprising way, that benzodioxine fused naphthopyrans possess particularly advantageous photochromic properties. More precisely, these compounds exhibit higher sensitivity to solar radiation and higher λmax values than the naphthopyran analogues, and possess, for certain derivatives, two intense absorption bands in the visible spectrum region. This type of photochromic molecules, which is novel per se, adapts well in association with other complementary photochromic dyes in order to give ray or brown tints.